Preservation of biopharmaceutical materials is important in the manufacture, storage, sale and use of such materials. For example, biopharmaceutical materials are often preserved by freezing between processing steps and during storage. Similarly, biopharmaceutical materials are often frozen during transportation between manufacturing locations.
Currently, preservation of biopharmaceutical material often involves placing a container containing liquid biopharmaceutical material in a cabinet freezer, chest freezer or walk-in freezer and allowing the biopharmaceutical material to freeze. Specifically, the container is often placed on a shelf in the cabinet freezer, chest freezer or walk-in freezer and the biopharmaceutical material is allowed to freeze. These containers may be stainless-steel vessels, plastic bottles or carboys, or plastic flexible containers. They are typically filled with a specified volume to allow for freezing and expansion and then transferred into the freezers at temperatures typically ranging from negative 20 degrees Celsius to negative 70 degrees Celsius or below.
To ensure efficient use of available space inside the freezer, containers are placed alongside one another and sometimes are stacked into an array with varied spatial regularity. Under these conditions, cooling of the biopharmaceutical solution occurs at different rates depending on the exposure of each container to the surrounding cold air, and the extent to which that container is shielded by neighboring containers. For example, containers placed close to the cooling source or those on the outside of an array of containers would be cooled more rapidly than those further away from the cooling source and/or situated at the interior of the array.
In general, adjacent placement of multiple containers in a freezer creates thermal differences from container to container. The freezing rate and product quality then depend on the actual freezer load, space between the containers, and air movement in the freezer. This results in a different thermal history for the contents of the containers depending on their location in a freezer, for example. Also, the use of different containers for individual portions of a single batch of biopharmaceutical material may cause different results for portions of the same batch due to different thermal histories resulting from freezing in a multiple container freezer, particularly if the storage arrangement is haphazard and random. Another consequence of obtaining a range of freezing times is that certain containers may freeze so slowly that the target solute can no longer be captured within the ice phase, but remains in a progressively smaller liquid phase. This phenomenon is referred to as “cyroconcentration.” In some cases such cyroconcentration could result in pH change, unfolding, aggregation, or precipitation of the biopharmaceutical product, thus resulting in product loss.
Disposable containers such as plastic flexible containers or other flexible containers often are damaged, leading to loss of the biopharmaceutical material. Particularly, the volumetric expansion of the biopharmaceutical materials during freezing could generate excessive pressure in an over filled bag or in a pocket of occluded liquid adjoining the bag material, possibly leading to rupture or damage to the integrity of the bag. Moreover, handling of such disposable containers, such as plastic flexible containers, during freezing, thawing, or transportation of these containers often result in damage thereof, due, for example, to shock, abrasion, impact, or other mishandling events arising from operator errors or inadequate protection of the flexible containers in use.
Thus, there is a need for systems and methods for freezing, storing, and thawing of biopharmaceutical materials that are controlled, do not result in loss of biopharmaceutical material, but instead create conditions conducive to preserving the biopharmaceutical material in a uniform, repeatable fashion in a protected environment.